Internal combustion engine

Abstract

An internal combustion engine is described that includes an expansion cylinder adjacent to a first combustion cylinder (or power cylinder). Combustion gases from the first cylinder are directed to the expansion cylinder to act on the piston in the expansion cylinder. The expansion cylinder has a larger bore (i.e. larger diameter piston) and/or a longer stroke than the first cylinder. The longer stroke also results in a much larger crankshaft arm resulting in a significantly improved mechanical advantage (i.e. torque). In addition, the expansion cylinder includes a check valve that is designed to automatically open the expansion chamber to atmosphere if a negative pressure develops due to the varying amount of exhaust gases at different speeds. In one embodiment, two power cylinders can be connected to one expansion cylinder.

The invention claimed is: 
     
       1. An internal combustion engine, comprising:
 a first cylinder with a first piston slidably disposed in the first cylinder, the first cylinder defining a combustion chamber having a first diameter; 
 the first piston having a first stroke; 
 an expansion cylinder adjacent to the first cylinder, with a second piston slidably disposed in the expansion cylinder, the expansion cylinder defining an expansion chamber having a second diameter; 
 the first piston of the first cylinder is between about 180-190 degrees out of phase with the second piston of the expansion cylinder; 
 an exhaust passage fluidly connecting the combustion chamber and the expansion chamber; 
 one or more valves controlling the flow of gas from the combustion chamber to the expansion chamber through the exhaust passage; 
 wherein the second diameter is larger than the first diameter and/or the second piston has a second stroke that is larger than the first stroke; 
 a vent passage on the expansion cylinder that fluidly communicates the expansion chamber with atmosphere, and a check valve on the expansion cylinder that controls flow through the vent passage, the check valve is biased by a spring to a closed position preventing flow through the vent passage, the check valve is movable against the bias of the spring to an open position so that the expansion cylinder fluidly communicates with atmosphere, and a spring force provided by the spring is such that the check valve automatically opens if a negative pressure develops in the expansion chamber so that atmospheric pressure is greater than the negative pressure in the expansion chamber to equalize pressure in the expansion chamber with atmospheric pressure. 
 
     
     
       2. The internal combustion engine of  claim 1 , wherein the second diameter is larger than the first diameter, and the second stroke of the second piston is larger than the first stroke. 
     
     
       3. The internal combustion engine of  claim 1 , wherein the one or more valves comprise a valve on the first cylinder that controls the flow of gas from the combustion chamber into the exhaust passage, and there is no valve on the expansion cylinder that controls the flow of gas from the exhaust passage into the expansion chamber. 
     
     
       4. An internal combustion engine, comprising:
 a first cylinder with a first piston slidably disposed in the first cylinder, the first cylinder defining a combustion chamber having a first diameter; 
 the first piston having a first stroke; 
 an expansion cylinder adjacent to the first cylinder, with a second piston slidably disposed in the expansion cylinder, the expansion cylinder defining an expansion chamber having a second diameter larger than the first diameter; 
 the second piston having a second stroke that is larger than the first stroke; 
 an exhaust passage fluidly connecting the combustion chamber and the expansion chamber; 
 one or more valves controlling the flow of gas from the combustion chamber to the expansion chamber through the exhaust passage; 
 the first piston of the first cylinder is between about 180-190 degrees out of phase with the second piston of the expansion cylinder; 
 an exhaust passageway at a top end of the expansion cylinder that is in fluid communication with the expansion chamber; 
 an exhaust valve in the exhaust passageway controlling flow through the exhaust passageway; 
 a vent passage at the top end of the expansion cylinder that fluidly communicates the expansion chamber with atmosphere, the vent passage is separate from the exhaust passageway; 
 a check valve in the vent passage that controls flow through the vent passage, the check valve is biased by a spring to a closed position preventing flow through the vent passage, the check valve is movable against the bias of the spring to an open position so that the expansion cylinder fluidly communicates with atmosphere, and a spring force provided by the spring is such that the check valve can automatically move to the open position when a pressure in the expansion chamber is less than atmospheric pressure. 
 
     
     
       5. The internal combustion engine of  claim 4 , wherein the one or more valves comprise a valve on the first cylinder that controls the flow of gas from the combustion chamber into the exhaust passage, and there is no valve on the expansion cylinder that controls the flow of gas from the exhaust passage into the expansion chamber.